Re: Coal Burning Power Plant.

[denison.8@osu.edu (Eric Denison)]

Stewart,

the numbers quoted in the prior message may be correct, but we can't know
for sure without knowing the elemental/chemical composition of the coal
being burned.  Your calculation seems to assume that both the unburned coal
and the remaining ash are pure carbon.  However, a measurable fraction of
the total coal mass will consist of impurities such as sulfur (responsible
for the sulfur dioxide and sulfuric acid consitiuents of the stack gas) and
daughter products from the uranium and thorium decay series.  In addition,
the fact that the ash mass is 20% of the fuel mass indicated that we've got
either a hell of a lot of impurities or incomplete oxidation of the
available carbon.  I'm guessing that the ash consists of a mish-mash of
partially-oxidized carbon species and the solid combustion products from
the impurities.  Since we don't have pure carbon going in as fuel or coming
out as ash, we can't calculate the CO2 yield simply from the mass
difference.

If someone has the data on the elemental/chemical composition of the fuel
used in the British plants, I'd be interested in seeing it.  We'd also need
some sort of data on the efficiency of the combustion process to calculate
the fractions of the carbon and impurities that go up the stack and stay in
the ash.

> A 2000 MW power station burns approximately 5,000,000 tons of coal each
> year.  This produces
>
> CO2                10,000,000 tons
> Ash                  1,000,000 tons >>
>
>The above numbers for C to CO2 seem incorrect. Given the 5,000,000 tons of
>coal to fire a 2,000 MW(e) plant which is right for reasonable capacity [80%
>of so], with 1,000,000 tons ash, this leaves about 4,000,000 tons of carbon.
>C combusted to CO2 changes mass from 12 to 44 or the ratio of CO2 to C is
>44/12=3.66. Thus the total CO2 produced should be about 4,000,0000 x 3.66 or
>about 14,666,000 tons not 10,000,000.
>
>What's wrong with the above math which shows the Nuclear Electric plc
>estimates for CO2 production to be low by about 32%?
>


J. Eric Denison
Nuclear Engineering Program
The Ohio State University
2030 Robinson Laboratory
206 West 18th Avenue
Columbus OH 43210
(614) 292-3681 or -1074
denison.8@osu.edu


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